1. Field of the Invention
This invention relates to a method of protecting crops from injury caused by application of herbicides and fungicides. More particularly, this invention relates to a method of applying to the crops in combination with the herbicides or fungicides an alkali lignin spray tank mix additive whose primary purpose is the reduction of phytotoxic effects of the herbicide or fungicide.
2. Description of the Prior Art
Chemical pesticides play a major role in promoting high crop yields. They also replace more expensive labor and mechanical methods for weed and pest control. For maximum utility in crop production, pesticides must have a high degree of selective toxicity, i.e., injury to undesirable plant species, fungi, and other pests but not to the desirable crops.
Selectivity may be governed by one or more factors including pesticide penetration, uptake, translocation, and metabolism. In some cases a crop is only marginally tolerant to herbicides required for the major weed problems and crop injury can often occur due to unusual weather conditions, interactions with other chemicals, crop varietal differences or errors in application. In the absence of a high degree of selective toxicity, steps must be taken to protect the desirable crop from the phytotoxic effect of the pesticide. An added degree of selectivity can often be achieved by critical timing of application, suitable placement of the pesticide, or use of chemical safening agents with the pesticide.
Although activated charcoal was perhaps the first material used as a pesticide safener, Belgian Pat. No. 619,202, in 1962, introduced the antidote concept. In this patent, Hoffman reduced carbamate herbicide damage to young grain plants by treating the seeds prior to planting with a non-phytotoxic amount of a hormone type growth regulant such as 4'-chloro- or 3',4'-dichloro-2-hydroxyiminoacetanilide. Also, Hoffman disclosed treating cereal seeds with nonphytotoxic amounts of 1,8-naphthalic anhydride to protect them from various herbicides in German Offenlegungsschrift No. 1,952,910.
Belgian Pat. No. 782,120, in 1972 disclosed N,N-diallyl-2,2-dichloroacetamide as an antidote-safener for thiocarbamate herbicide. This material may be included in the herbicide formulation and applied with the herbicide treatment. Subsequently, various other compounds have been found to be antidote-safeners for herbicides. However, such antidotes chemically modify the pesticides to counteract its poisonous effects. In a broader context a pesticide safener is any substance which prevents objectionable changes to the crop upon exposure to the pesticide. Thus, a safener, or phytotoxicity reducer, is not necessarily an antidote.
It is the general object of this invention to provide a lignin based pesticide safener which inhibits the exposure of the pesticide to reduce its phytotoxic effects.
The use of lignins in pesticide formulations as a surfactant or as part of the pesticide delivery system is known.
In U.S. Pat. No. 3,726,850, Detroit teaches water-soluble, ozone-oxidized alkali lignin to be pesticide dispersants. U.S. Pat. No. 3,992,532 discloses a method for providing a flowable pesticide formulation with such rheological properties so as to reduce or eliminate sedimentation and liquid phase separation of insoluble pesticides by mixing alkali lignin and liquid toxicant with a hydrocarbon oil and subjecting the mixture to high shear.
U.S. Pat. No. 3,813,236 discloses the chemical covalent bonding of a pesticide to a lignin polymeric substrate. The pesticide is controllably released by destruction of the covalent chemical bonds. U.S. Pat. No. 3,929,453, reissued as Re 29,238, teaches a slow release lignin composite obtained by the coprecipitation-inclusion from an aqueous alkaline lignin solution by adding acid or salts, the drying of a precipitated lignin slurry/pesticide dispersion, or the elimination of a common solvent from a lignin-pesticide mixture.
In other sustained release compositions, U.S. Pat. Nos. 4,184,866, 4,244,728 and 4,244,729, all of which have as a co-inventor a co-inventor in this application, teach an improved pesticide carrier made by cross-linking an alkali lignin with epichlorohydrin or formaldehyde.
It is the particular object of this invention to provide an alkali lignin-pesticide combination suitable for spray application which combination has a reduced phytotoxic effect than that resulting from application of the pesticide alone. It is a further object of this invention to provide a water-insoluble alkali lignin based spray tank mix additive which, when mixed with the pesticide prior to application, reduces the phytotoxic effect of the pesticide. It is a still further object of the invention to provide a method for protecting crops from injury caused by application of a pesticide selected from the group consisting of herbicides, fungicides and insecticides, the method comprising applying to the crops in combination with the pesticide a phytotoxicity reducing amount of water-insoluble alkali lignin.